When hive.cache.expr.evaluation is set to true (which is the default) a UDF can give incorrect results if it is nested in another UDF or a Hive function. This bug affects releases 0.12.0, 0.13.0, and 0.13.1. Release 0.14.0 fixed the bug (HIVE-7314).

The problem relates to the UDF's implementation of the getDisplayString method, as discussed in the Hive user mailing list.

Built-in Operators

Operators Precedences

Example

Operators

Description

A[B] , A.identifier

bracket_op([]), dot(.)

element selector, dot

-A

unary(+), unary(-), unary(~)

unary prefix operators

A IS (NOT) NULL

IS NULL,IS NOT NULL

unary suffix

A ^ B

bitwise xor(^)

bitwise xor

A * B

star(*), divide(/), mod(%), div(DIV)

multiplicative operators

A + B

plus(+), minus(-)

additive operators

A || B

string concatenate(||)

string concatenate

A & B

bitwise and(&)

bitwise and

A | B

bitwise or(|)

bitwise or

Relational Operators

The following operators compare the passed operands and generate a TRUE or FALSE value depending on whether the comparison between the operands holds.

Operator

Operand types

Description

A = B

All primitive types

TRUE if expression A is equal to expression B otherwise FALSE.

A == B

All primitive types

Synonym for the = operator.

A <=> B

All primitive types

Returns same result with EQUAL(=) operator for non-null operands, but returns TRUE if both are NULL, FALSE if one of the them is NULL. (As of version 0.9.0.)

A <> B

All primitive types

NULL if A or B is NULL, TRUE if expression A is NOT equal to expression B, otherwise FALSE.

A != B

All primitive types

Synonym for the <> operator.

A < B

All primitive types

NULL if A or B is NULL, TRUE if expression A is less than expression B, otherwise FALSE.

A <= B

All primitive types

NULL if A or B is NULL, TRUE if expression A is less than or equal to expression B, otherwise FALSE.

A > B

All primitive types

NULL if A or B is NULL, TRUE if expression A is greater than expression B, otherwise FALSE.

A >= B

All primitive types

NULL if A or B is NULL, TRUE if expression A is greater than or equal to expression B, otherwise FALSE.

A [NOT] BETWEEN B AND C

All primitive types

NULL if A, B or C is NULL, TRUE if A is greater than or equal to B AND A less than or equal to C, otherwise FALSE. This can be inverted by using the NOT keyword. (As of version 0.9.0.)

A IS NULL

All types

TRUE if expression A evaluates to NULL, otherwise FALSE.

A IS NOT NULL

All types

FALSE if expression A evaluates to NULL, otherwise TRUE.

A [NOT] LIKE B

strings

NULL if A or B is NULL, TRUE if string A matches the SQL simple regular expression B, otherwise FALSE. The comparison is done character by character. The _ character in B matches any character in A (similar to . in posix regular expressions) while the % character in B matches an arbitrary number of characters in A (similar to .* in posix regular expressions). For example, 'foobar' like 'foo' evaluates to FALSE whereas 'foobar' like 'foo_ _ _' evaluates to TRUE and so does 'foobar' like 'foo%'.

A RLIKE B

strings

NULL if A or B is NULL, TRUE if any (possibly empty) substring of A matches the Java regular expression B, otherwise FALSE. For example, 'foobar' RLIKE 'foo' evaluates to TRUE and so does 'foobar' RLIKE '^f.*r$'.

A REGEXP B

strings

Same as RLIKE.

Arithmetic Operators

The following operators support various common arithmetic operations on the operands. All return number types; if any of the operands are NULL, then the result is also NULL.

Operator

Operand types

Description

A + B

All number types

Gives the result of adding A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. For example since every integer is a float, therefore float is a containing type of integer so the + operator on a float and an int will result in a float.

A - B

All number types

Gives the result of subtracting B from A. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands.

A * B

All number types

Gives the result of multiplying A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands. Note that if the multiplication causing overflow, you will have to cast one of the operators to a type higher in the type hierarchy.

A / B

All number types

Gives the result of dividing A by B. The result is a double type in most cases. When A and B are both integers, the result is a double type except when the hive.compat configuration parameter is set to "0.13" or "latest" in which case the result is a decimal type.

A DIV B

Integer types

Gives the integer part resulting from dividing A by B. E.g 17 div 3 results in 5.

A % B

All number types

Gives the reminder resulting from dividing A by B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands.

A & B

All number types

Gives the result of bitwise AND of A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands.

A | B

All number types

Gives the result of bitwise OR of A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands.

A ^ B

All number types

Gives the result of bitwise XOR of A and B. The type of the result is the same as the common parent(in the type hierarchy) of the types of the operands.

~A

All number types

Gives the result of bitwise NOT of A. The type of the result is the same as the type of A.

Logical Operators

The following operators provide support for creating logical expressions. All of them return boolean TRUE, FALSE, or NULL depending upon the boolean values of the operands. NULL behaves as an "unknown" flag, so if the result depends on the state of an unknown, the result itself is unknown.

Operator

Operand types

Description

A AND B

boolean

TRUE if both A and B are TRUE, otherwise FALSE. NULL if A or B is NULL.

A OR B

boolean

TRUE if either A or B or both are TRUE, FALSE OR NULL is NULL, otherwise FALSE.

NOT A

boolean

TRUE if A is FALSE or NULL if A is NULL. Otherwise FALSE.

! A

boolean

Same as NOT A.

A IN (val1, val2, ...)

boolean

TRUE if A is equal to any of the values. As of Hive 0.13 subqueries are supported in IN statements.

A NOT IN (val1, val2, ...)

boolean

TRUE if A is not equal to any of the values. As of Hive 0.13 subqueries are supported in NOT IN statements.

[NOT] EXISTS (subquery)

TRUE if the the subquery returns at least one row. Supported as of Hive 0.13.

String Operators

Operator

Operand types

Description

A || B

strings

Concatenates the operands - shorthand for concat(A,B) . Supported as of Hive 2.2.0.

Complex Type Constructors

The following functions construct instances of complex types.

Constructor Function

Operands

Description

map

(key1, value1, key2, value2, ...)

Creates a map with the given key/value pairs.

struct

(val1, val2, val3, ...)

Creates a struct with the given field values. Struct field names will be col1, col2, ....

named_struct

(name1, val1, name2, val2, ...)

Creates a struct with the given field names and values. (As of Hive 0.8.0.)

array

(val1, val2, ...)

Creates an array with the given elements.

create_union

(tag, val1, val2, ...)

Creates a union type with the value that is being pointed to by the tag parameter.

Operators on Complex Types

The following operators provide mechanisms to access elements in Complex Types.

Operator

Operand types

Description

A[n]

A is an Array and n is an int

Returns the nth element in the array A. The first element has index 0. For example, if A is an array comprising of ['foo', 'bar'] then A[0] returns 'foo' and A[1] returns 'bar'.

M[key]

M is a Map<K, V> and key has type K

Returns the value corresponding to the key in the map. For example, if M is a map comprising of {'f' -> 'foo', 'b' -> 'bar', 'all' -> 'foobar'} then M['all'] returns 'foobar'.

S.x

S is a struct

Returns the x field of S. For example for the struct foobar {int foo, int bar}, foobar.foo returns the integer stored in the foo field of the struct.

Built-in Functions

Mathematical Functions

The following built-in mathematical functions are supported in Hive; most return NULL when the argument(s) are NULL:

Returns the greatest value of the list of values (as of Hive 1.1.0). Fixed to return NULL when one or more arguments are NULL, and strict type restriction relaxed, consistent with ">" operator (as of Hive 2.0.0).

T

least(T v1, T v2, ...)

Returns the least value of the list of values (as of Hive 1.1.0). Fixed to return NULL when one or more arguments are NULL, and strict type restriction relaxed, consistent with "<" operator (as of Hive 2.0.0).

Mathematical Functions and Operators for Decimal Datatypes

All regular arithmetic operators (such as +, -, *, /) and relevant mathematical UDFs (Floor, Ceil, Round, and many more) have been updated to handle decimal types. For a list of supported UDFs, see Mathematical UDFs in Hive Data Types.

Collection Functions

The following built-in collection functions are supported in Hive:

Return Type

Name(Signature)

Description

int

size(Map<K.V>)

Returns the number of elements in the map type.

int

size(Array<T>)

Returns the number of elements in the array type.

array<K>

map_keys(Map<K.V>)

Returns an unordered array containing the keys of the input map.

array<V>

map_values(Map<K.V>)

Returns an unordered array containing the values of the input map.

boolean

array_contains(Array<T>, value)

Returns TRUE if the array contains value.

array<t>

sort_array(Array<T>)

Sorts the input array in ascending order according to the natural ordering of the array elements and returns it (as of version 0.9.0).

Type Conversion Functions

The following type conversion functions are supported in Hive:

Return Type

Name(Signature)

Description

binary

binary(string|binary)

Casts the parameter into a binary.

Expected "=" to follow "type"

cast(expr as <type>)

Converts the results of the expression expr to <type>. For example, cast('1' as BIGINT) will convert the string '1' to its integral representation. A null is returned if the conversion does not succeed. If cast(expr as boolean) Hive returns true for a non-empty string.

Date Functions

The following built-in date functions are supported in Hive:

Return Type

Name(Signature)

Description

string

from_unixtime(bigint unixtime[, string format])

Converts the number of seconds from unix epoch (1970-01-01 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the format of "1970-01-01 00:00:00".

bigint

unix_timestamp()

Gets current Unix timestamp in seconds. This function is not deterministic and its value is not fixed for the scope of a query execution, therefore prevents proper optimization of queries - this has been deprecated since 2.0 in favour of CURRENT_TIMESTAMP constant.

Retrieve fields such as days or hours from source (as of Hive 2.2.0). Source must be a date, timestamp, interval or a string that can be converted into either a date or timestamp. Supported fields include: day, dayofweek, hour, minute, month, quarter, second, week and year.

Examples:

select extract(month from "2016-10-20") results in 10.

select extract(hour from "2016-10-20 05:06:07") results in 5.

select extract(dayofweek from "2016-10-20 05:06:07") results in 5.

select extract(month from interval '1-3' year to month) results in 3.

select extract(minute from interval '3 12:20:30' day to second) results in 20.

int

datediff(string enddate, string startdate)

Returns the number of days from startdate to enddate: datediff('2009-03-01', '2009-02-27') = 2.

pre 2.1.0: string

2.1.0 on: date

date_add(date/timestamp/string startdate, tinyint/smallint/int days)

Adds a number of days to startdate: date_add('2008-12-31', 1) = '2009-01-01'.

Prior to Hive 2.1.0 (HIVE-13248) the return type was a String because no Date type existed when the method was created.

pre 2.1.0: string

2.1.0 on: date

date_sub(date/timestamp/string startdate, tinyint/smallint/int days)

Subtracts a number of days to startdate: date_sub('2008-12-31', 1) = '2008-12-30'.

Prior to Hive 2.1.0 (HIVE-13248) the return type was a String because no Date type existed when the method was created.

timestamp

from_utc_timestamp({any primitive type}*, string timezone)

Assumes given timestamp is UTC and converts to given timezone (as of Hive 0.8.0). For example, from_utc_timestamp('1970-01-01 08:00:00','PST') returns 1970-01-01 00:00:00.

Returns the current date at the start of query evaluation (as of Hive 1.2.0). All calls of current_date within the same query return the same value.

timestamp

current_timestamp

Returns the current timestamp at the start of query evaluation (as of Hive 1.2.0). All calls of current_timestamp within the same query return the same value.

string

add_months(string start_date, int num_months)

Returns the date that is num_months after start_date (as of Hive 1.1.0). start_date is a string, date or timestamp. num_months is an integer. The time part of start_date is ignored. If start_date is the last day of the month or if the resulting month has fewer days than the day component of start_date, then the result is the last day of the resulting month. Otherwise, the result has the same day component as start_date.

string

last_day(string date)

Returns the last day of the month which the date belongs to (as of Hive 1.1.0). date is a string in the format 'yyyy-MM-dd HH:mm:ss' or 'yyyy-MM-dd'. The time part of date is ignored.

string

next_day(string start_date, string day_of_week)

Returns the first date which is later than start_date and named as day_of_week (as of Hive 1.2.0). start_date is a string/date/timestamp. day_of_week is 2 letters, 3 letters or full name of the day of the week (e.g. Mo, tue, FRIDAY). The time part of start_date is ignored. Example: next_day('2015-01-14', 'TU') = 2015-01-20.

Returns number of months between dates date1 and date2 (as of Hive1.2.0). If date1 is later than date2, then the result is positive. If date1 is earlier than date2, then the result is negative. If date1 and date2 are either the same days of the month or both last days of months, then the result is always an integer. Otherwise the UDF calculates the fractional portion of the result based on a 31-day month and considers the difference in time components date1 and date2. date1 and date2 type can be date, timestamp or string in the format 'yyyy-MM-dd' or 'yyyy-MM-dd HH:mm:ss'. The result is rounded to 8 decimal places. Example: months_between('1997-02-28 10:30:00', '1996-10-30') = 3.94959677

Throw an exception if 'condition' is not true, otherwise return null (as of Hive 0.8.0). For example, select assert_true (2<1).

String Functions

The following built-in String functions are supported in Hive:

Return Type

Name(Signature)

Description

int

ascii(string str)

Returns the numeric value of the first character of str.

string

base64(binary bin)

Converts the argument from binary to a base 64 string (as of Hive 0.12.0).

int

character_length(string str)

Returns the number of UTF-8 characters contained in str (as of Hive 2.2.0). The function char_length is shorthand for this function.

string

chr(bigint|double A)

Returns the ASCII character having the binary equivalent to A (as of Hive 1.3.0 and 2.1.0). If A is larger than 256 the result is equivalent to chr(A % 256). Example: select chr(88); returns "X".

string

concat(string|binary A, string|binary B...)

Returns the string or bytes resulting from concatenating the strings or bytes passed in as parameters in order. For example, concat('foo', 'bar') results in 'foobar'. Note that this function can take any number of input strings.

array<struct<string,double>>

context_ngrams(array<array<string>>, array<string>, int K, int pf)

Returns the top-k contextual N-grams from a set of tokenized sentences, given a string of "context". See StatisticsAndDataMining for more information.

string

concat_ws(string SEP, string A, string B...)

Like concat() above, but with custom separator SEP.

string

concat_ws(string SEP, array<string>)

Like concat_ws() above, but taking an array of strings. (as of Hive 0.9.0)

string

decode(binary bin, string charset)

Decodes the first argument into a String using the provided character set (one of 'US-ASCII', 'ISO-8859-1', 'UTF-8', 'UTF-16BE', 'UTF-16LE', 'UTF-16'). If either argument is null, the result will also be null. (As of Hive 0.12.0.)

string

elt(N int,str1 string,str2 string,str3 string,...)

Return string at index number. For example elt(2,'hello','world') returns 'world'. Returns NULL if N is less than 1 or greater than the number of arguments.

Encodes the first argument into a BINARY using the provided character set (one of 'US-ASCII', 'ISO-8859-1', 'UTF-8', 'UTF-16BE', 'UTF-16LE', 'UTF-16'). If either argument is null, the result will also be null. (As of Hive 0.12.0.)

int

field(val T,val1 T,val2 T,val3 T,...)

Returns the index of val in the val1,val2,val3,... list or 0 if not found. For example field('world','say','hello','world') returns 3.All primitive types are supported, arguments are compared using str.equals(x). If val is NULL, the return value is 0.

Returns the first occurance of str in strList where strList is a comma-delimited string. Returns null if either argument is null. Returns 0 if the first argument contains any commas. For example, find_in_set('ab', 'abc,b,ab,c,def') returns 3.

string

format_number(number x, int d)

Formats the number X to a format like '#,###,###.##', rounded to D decimal places, and returns the result as a string. If D is 0, the result has no decimal point or fractional part. (As of Hive 0.10.0; bug with float types fixed in Hive 0.14.0, decimal type support added in Hive 0.14.0)

string

get_json_object(string json_string, string path)

Extracts json object from a json string based on json path specified, and returns json string of the extracted json object. It will return null if the input json string is invalid. NOTE: The json path can only have the characters [0-9a-z_], i.e., no upper-case or special characters. Also, the keys *cannot start with numbers.* This is due to restrictions on Hive column names.

boolean

in_file(string str, string filename)

Returns true if the string str appears as an entire line in filename.

int

instr(string str, string substr)

Returns the position of the first occurrence of substr in str. Returns null if either of the arguments are null and returns 0 if substr could not be found in str. Be aware that this is not zero based. The first character in str has index 1.

int

length(string A)

Returns the length of the string.

int

locate(string substr, string str[, int pos])

Returns the position of the first occurrence of substr in str after position pos.

string

lower(string A) lcase(string A)

Returns the string resulting from converting all characters of B to lower case. For example, lower('fOoBaR') results in 'foobar'.

string

lpad(string str, int len, string pad)

Returns str, left-padded with pad to a length of len. If str is longer than len, the return value is shortened to len characters. In case of empty pad string, the return value is null.

string

ltrim(string A)

Returns the string resulting from trimming spaces from the beginning(left hand side) of A. For example, ltrim(' foobar ') results in 'foobar '.

array<struct<string,double>>

ngrams(array<array<string>>, int N, int K, int pf)

Returns the top-k N-grams from a set of tokenized sentences, such as those returned by the sentences() UDAF. See StatisticsAndDataMining for more information.

int

octet_length(string str)

Returns the number of octets required to hold the string str in UTF-8 encoding (since Hive 2.2.0). Note that octet_length(str) can be larger than character_length(str).

Returns the specified part from the URL. Valid values for partToExtract include HOST, PATH, QUERY, REF, PROTOCOL, AUTHORITY, FILE, and USERINFO. For example, parse_url('http://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'HOST') returns 'facebook.com'. Also a value of a particular key in QUERY can be extracted by providing the key as the third argument, for example, parse_url('http://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'QUERY', 'k1') returns 'v1'.

string

printf(String format, Obj... args)

Returns the input formatted according do printf-style format strings (as of Hive 0.9.0).

string

regexp_extract(string subject, string pattern, int index)

Returns the string extracted using the pattern. For example, regexp_extract('foothebar', 'foo(.*?)(bar)', 2) returns 'bar.' Note that some care is necessary in using predefined character classes: using '\s' as the second argument will match the letter s; '\\s' is necessary to match whitespace, etc. The 'index' parameter is the Java regex Matcher group() method index. See docs/api/java/util/regex/Matcher.html for more information on the 'index' or Java regex group() method.

Returns the string resulting from replacing all substrings in INITIAL_STRING that match the java regular expression syntax defined in PATTERN with instances of REPLACEMENT. For example, regexp_replace("foobar", "oo|ar", "") returns 'fb.' Note that some care is necessary in using predefined character classes: using '\s' as the second argument will match the letter s; '\\s' is necessary to match whitespace, etc.

string

repeat(string str, int n)

Repeats str n times.

string

replace(string A, string OLD, string NEW)

Returns the string A with all non-overlapping occurrences of OLD replaced with NEW (as of Hive 1.3.0 and 2.1.0). Example: select replace("ababab", "abab", "Z"); returns "Zab".

string

reverse(string A)

Returns the reversed string.

string

rpad(string str, int len, string pad)

Returns str, right-padded with pad to a length of len. If str is longer than len, the return value is shortened to len characters. In case of empty pad string, the return value is null.

string

rtrim(string A)

Returns the string resulting from trimming spaces from the end(right hand side) of A. For example, rtrim(' foobar ') results in ' foobar'.

array<array<string>>

sentences(string str, string lang, string locale)

Tokenizes a string of natural language text into words and sentences, where each sentence is broken at the appropriate sentence boundary and returned as an array of words. The 'lang' and 'locale' are optional arguments. For example, sentences('Hello there! How are you?') returns ( ("Hello", "there"), ("How", "are", "you") ).

string

space(int n)

Returns a string of n spaces.

array

split(string str, string pat)

Splits str around pat (pat is a regular expression).

map<string,string>

str_to_map(text[, delimiter1, delimiter2])

Splits text into key-value pairs using two delimiters. Delimiter1 separates text into K-V pairs, and Delimiter2 splits each K-V pair. Default delimiters are ',' for delimiter1 and ':' for delimiter2.

Returns the substring from string A before count occurrences of the delimiter delim (as of Hive 1.3.0). If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. Substring_index performs a case-sensitive match when searching for delim. Example: substring_index('www.apache.org', '.', 2) = 'www.apache'.

Translates the input string by replacing the characters present in the from string with the corresponding characters in the to string. This is similar to the translate function in PostgreSQL. If any of the parameters to this UDF are NULL, the result is NULL as well. (Available as of Hive 0.10.0, for string types)

Returns the string resulting from trimming spaces from both ends of A. For example, trim(' foobar ') results in 'foobar'

binary

unbase64(string str)

Converts the argument from a base 64 string to BINARY. (As of Hive 0.12.0.)

string

upper(string A) ucase(string A)

Returns the string resulting from converting all characters of A to upper case. For example, upper('fOoBaR') results in 'FOOBAR'.

string

initcap(string A)

Returns string, with the first letter of each word in uppercase, all other letters in lowercase. Words are delimited by whitespace. (As of Hive 1.1.0.)

int

levenshtein(string A, string B)

Returns the Levenshtein distance between two strings (as of Hive 1.2.0). For example, levenshtein('kitten', 'sitting') results in 3.

string

soundex(string A)

Returns soundex code of the string (as of Hive 1.2.0). For example, soundex('Miller') results in M460.

Data Masking Functions

The following built-in data masking functions are supported in Hive:

Return Type

Name(Signature)

Description

string

mask(string str[, string upper[, string lower[, string number]]])

Returns a masked version of str (as of Hive 2.1.0). By default, upper case letters are converted to "X", lower case letters are converted to "x" and numbers are converted to "n". For example mask("abcd-EFGH-8765-4321") results in xxxx-XXXX-nnnn-nnnn. You can override the characters used in the mask by supplying additional arguments: the second argument controls the mask character for upper case letters, the third argument for lower case letters and the fourth argument for numbers. For example, mask("abcd-EFGH-8765-4321", "U", "l", "#") results in llll-UUUU-####-####.

string

mask_first_n(string str[, int n])

Returns a masked version of str with the first n values masked (as of Hive 2.1.0). Upper case letters are converted to "X", lower case letters are converted to "x" and numbers are converted to "n". For example, mask_first_n("1234-5678-8765-4321", 4) results in nnnn-5678-8765-4321.

string

mask_last_n(string str[, int n])

Returns a masked version of str with the last n values masked (as of Hive 2.1.0). Upper case letters are converted to "X", lower case letters are converted to "x" and numbers are converted to "n". For example, mask_last_n("1234-5678-8765-4321", 4) results in 1234-5678-8765-nnnn.

string

mask_show_first_n(string str[, int n])

Returns a masked version of str, showing the first n characters unmasked (as of Hive 2.1.0). Upper case letters are converted to "X", lower case letters are converted to "x" and numbers are converted to "n". For example, mask_show_first_n("1234-5678-8765-4321", 4) results in 1234-nnnn-nnnn-nnnn.

string

mask_show_last_n(string str[, int n])

Returns a masked version of str, showing the last n characters unmasked (as of Hive 2.1.0). Upper case letters are converted to "X", lower case letters are converted to "x" and numbers are converted to "n". For example, mask_show_last_n("1234-5678-8765-4321", 4) results in nnnn-nnnn-nnnn-4321.

string

mask_hash(string|char|varchar str)

Returns a hashed value based on str (as of Hive 2.1.0). The hash is consistent and can be used to join masked values together across tables. This function returns null for non-string types.

Misc. Functions

Calls a Java method by matching the argument signature, using reflection. (As of Hive 0.7.0.) See Reflect (Generic) UDF for examples.

int

hash(a1[, a2...])

Returns a hash value of the arguments. (As of Hive 0.4.)

string

current_user()

Returns current user name from the configured authenticator manager (as of Hive 1.2.0). Could be the same as the user provided when connecting, but with some authentication managers (for example HadoopDefaultAuthenticator) it could be different.

string

logged_in_user()

Returns current user name from the session state (as of Hive 2.2.0). This is the username provided when connecting to Hive.

Calculates an MD5 128-bit checksum for the string or binary (as of Hive 1.3.0). The value is returned as a string of 32 hex digits, or NULL if the argument was NULL. Example: md5('ABC') = '902fbdd2b1df0c4f70b4a5d23525e932'.

string

sha1(string/binary)

sha(string/binary)

Calculates the SHA-1 digest for string or binary and returns the value as a hex string (as of Hive 1.3.0). Example: sha1('ABC') = '3c01bdbb26f358bab27f267924aa2c9a03fcfdb8'.

Calculates the SHA-2 family of hash functions (SHA-224, SHA-256, SHA-384, and SHA-512) (as of Hive 1.3.0). The first argument is the string or binary to be hashed. The second argument indicates the desired bit length of the result, which must have a value of 224, 256, 384, 512, or 0 (which is equivalent to 256). SHA-224 is supported starting from Java 8. If either argument is NULL or the hash length is not one of the permitted values, the return value is NULL. Example: sha2('ABC', 256) = 'b5d4045c3f466fa91fe2cc6abe79232a1a57cdf104f7a26e716e0a1e2789df78'.

binary

aes_encrypt(input string/binary, key string/binary)

Encrypt input using AES (as of Hive 1.3.0). Key lengths of 128, 192 or 256 bits can be used. 192 and 256 bits keys can be used if Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files are installed. If either argument is NULL or the key length is not one of the permitted values, the return value is NULL. Example: base64(aes_encrypt('ABC', '1234567890123456')) = 'y6Ss+zCYObpCbgfWfyNWTw=='.

binary

aes_decrypt(input binary, key string/binary)

Decrypt input using AES (as of Hive 1.3.0). Key lengths of 128, 192 or 256 bits can be used. 192 and 256 bits keys can be used if Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files are installed. If either argument is NULL or the key length is not one of the permitted values, the return value is NULL. Example: aes_decrypt(unbase64('y6Ss+zCYObpCbgfWfyNWTw=='), '1234567890123456') = 'ABC'.

string

version()

Returns the Hive version (as of Hive 2.1.0). The string contains 2 fields, the first being a build number and the second being a build hash. Example: "select version();" might return "2.1.0.2.5.0.0-1245 r027527b9c5ce1a3d7d0b6d2e6de2378fb0c39232". Actual results will depend on your build.

Built-in Aggregate Functions (UDAF)

count(*) - Returns the total number of retrieved rows, including rows containing NULL values.

count(expr) - Returns the number of rows for which the supplied expression is non-NULL.

count(DISTINCT expr[, expr]) - Returns the number of rows for which the supplied expression(s) are unique and non-NULL. Execution of this can be optimized with hive.optimize.distinct.rewrite.

DOUBLE

sum(col), sum(DISTINCT col)

Returns the sum of the elements in the group or the sum of the distinct values of the column in the group.

DOUBLE

avg(col), avg(DISTINCT col)

Returns the average of the elements in the group or the average of the distinct values of the column in the group.

DOUBLE

min(col)

Returns the minimum of the column in the group.

DOUBLE

max(col)

Returns the maximum value of the column in the group.

DOUBLE

variance(col), var_pop(col)

Returns the variance of a numeric column in the group.

DOUBLE

var_samp(col)

Returns the unbiased sample variance of a numeric column in the group.

DOUBLE

stddev_pop(col)

Returns the standard deviation of a numeric column in the group.

DOUBLE

stddev_samp(col)

Returns the unbiased sample standard deviation of a numeric column in the group.

DOUBLE

covar_pop(col1, col2)

Returns the population covariance of a pair of numeric columns in the group.

DOUBLE

covar_samp(col1, col2)

Returns the sample covariance of a pair of a numeric columns in the group.

DOUBLE

corr(col1, col2)

Returns the Pearson coefficient of correlation of a pair of a numeric columns in the group.

DOUBLE

percentile(BIGINT col, p)

Returns the exact pth percentile of a column in the group (does not work with floating point types). p must be between 0 and 1. NOTE: A true percentile can only be computed for integer values. Use PERCENTILE_APPROX if your input is non-integral.

array<double>

percentile(BIGINT col, array(p1 [, p2]...))

Returns the exact percentiles p1, p2, ... of a column in the group (does not work with floating point types). pi must be between 0 and 1. NOTE: A true percentile can only be computed for integer values. Use PERCENTILE_APPROX if your input is non-integral.

DOUBLE

percentile_approx(DOUBLE col, p [, B])

Returns an approximate pth percentile of a numeric column (including floating point types) in the group. The B parameter controls approximation accuracy at the cost of memory. Higher values yield better approximations, and the default is 10,000. When the number of distinct values in col is smaller than B, this gives an exact percentile value.

array<double>

percentile_approx(DOUBLE col, array(p1 [, p2]...) [, B])

Same as above, but accepts and returns an array of percentile values instead of a single one.

Divides an ordered partition into x groups called buckets and assigns a bucket number to each row in the partition. This allows easy calculation of tertiles, quartiles, deciles, percentiles and other common summary statistics. (As of Hive 0.11.0.)

Built-in Table-Generating Functions (UDTF)

Normal user-defined functions, such as concat(), take in a single input row and output a single output row. In contrast, table-generating functions transform a single input row to multiple output rows.

Return Type

Name(Signature)

Description

N rows

explode(ARRAY)

Returns one row for each element from the array.

N rows

explode(MAP)

Returns one row for each key-value pair from the input map with two columns in each row: one for the key and another for the value. (As of Hive 0.8.0.)

posexplode

posexplode() is similar to explode but instead of just returning the elements of the array it returns the element as well as its position in the original array.

As an example of using posexplode() in the SELECT expression list, consider a table named myTable that has a single column (myCol) and two rows:

Array<int> myCol

[100,200,300]

[400,500,600]

Then running the query:

will produce:

(int) pos

(int) myNewCol

1

100

2

200

3

300

1

400

2

500

3

600

json_tuple

A new json_tuple() UDTF is introduced in Hive 0.7. It takes a set of names (keys) and a JSON string, and returns a tuple of values using one function. This is much more efficient than calling GET_JSON_OBJECT to retrieve more than one key from a single JSON string. In any case where a single JSON string would be parsed more than once, your query will be more efficient if you parse it once, which is what JSON_TUPLE is for. As JSON_TUPLE is a UDTF, you will need to use the LATERAL VIEW syntax in order to achieve the same goal.

For example,

should be changed to:

parse_url_tuple

The parse_url_tuple() UDTF is similar to parse_url(), but can extract multiple parts of a given URL, returning the data in a tuple. Values for a particular key in QUERY can be extracted by appending a colon and the key to the partToExtract argument, for example, parse_url_tuple('http://facebook.com/path1/p.php?k1=v1&k2=v2#Ref1', 'QUERY:k1', 'QUERY:k2') returns a tuple with values of 'v1','v2'. This is more efficient than calling parse_url() multiple times. All the input parameters and output column types are string.

GROUPing and SORTing on f(column)

A typical OLAP pattern is that you have a timestamp column and you want to group by daily or other less granular date windows than by second. So you might want to select concat(year(dt),month(dt)) and then group on that concat(). But if you attempt to GROUP BY or SORT BY a column on which you've applied a function and alias, like this:

you will get an error:

because you are not able to GROUP BY or SORT BY a column alias on which a function has been applied. There are two workarounds. First, you can reformulate this query with subqueries, which is somewhat complicated:

Or you can make sure not to use a column alias, which is simpler:

Contact Tim Ellis (tellis) at RiotGames dot com if you would like to discuss this in further detail.

UDF internals

The context of a UDF's evaluate method is one row at a time. A simple invocation of a UDF like

would evaluate the length of each of the string_col's values in the map portion of the job. The side effect of the UDF being evaluated on the map-side is that you can't control the order of rows which get sent to the mapper. It is the same order in which the file split sent to the mapper gets deserialized. Any reduce side operation (such as SORT BY, ORDER BY, regular JOIN, etc.) would apply to the UDFs output as if it is just another column of the table. This is fine since the context of the UDF's evaluate method is meant to be one row at a time.

If you would like to control which rows get sent to the same UDF (and possibly in what order), you will have the urge to make the UDF evaluate during the reduce phase. This is achievable by making use of DISTRIBUTE BY, DISTRIBUTE BY + SORT BY, CLUSTER BY. An example query would be:

However, one could argue that the very premise of your requirement to control the set of rows sent to the same UDF is to do aggregation in that UDF. In such a case, using a User Defined Aggregate Function (UDAF) is a better choice. You can read more about writing a UDAF here. Alternatively, you can user a custom reduce script to accomplish the same using Hive's Transform functionality. Both of these options would do aggregations on the reduce side.